From the Economist:
Rape in war is as old as war itself. After the sack of Rome 16 centuries ago Saint Augustine called rape in wartime an “ancient and customary evil”. For soldiers, it has long been considered one of the spoils of war.
In 2008 the UN Security Council officially acknowledged that rape has been used as a tool of war. With these kinds of resolutions and global campaigns against rape in war, the world has become more sensitive. At least in theory, the Geneva Conventions, governing the treatment of civilians in war, are respected by politicians and generals in most decent states. Generals from rich countries know that their treatment of civilians in the theatre of war comes under ever closer scrutiny. The laws and customs of war are clear. But in many parts of the world, in the Hobbesian anarchy of irregular war, with ill-disciplined private armies or militias, these norms carry little weight.